As different types of residential lighting have evolved so, too, have different types of light bulbs. Apart from major differences such as incandescent versus fluorescent, different base styles have been introduced including, Edison, candelabra and prong-type connectors for halogen. See, for example, www.donsbulbs.com. In addition to these differences, power ratings vary substantially from a few watts to hundreds of watts.
The plethora of different bulb types makes shopping for bulbs problematic, in that one must make an inventory of each type and style required, while keeping track of the maximum usable power for a particular fixture.
Various adapters have been proposed to allow a lamp socket to accommodate more than one type of bulb. Some of these inventions date back more than a hundred years. As one example, U.S. Pat. No. 1,172,953, is directed to “adapters for enabling an electric lamp or the like to be operated at its rated or any desired voltage in a socket or receptacle between whose terminals some different voltage prevails.” As shown in FIG. 1, the patent discloses a unitary structure having a base 10 for a screw-in socket, a receptacle 16 for a lamp having a bayonet-type base, and means such as a transformer for producing the desired voltage between the terminals or contacts of the receptacle.
As electrical solutions have given way to electronic implementations, transformers have been replaced in some cases with solid-state dimmers. An early version, disclosed in U.S. Pat. No. 3,517,259 (FIG. 2), describes a lamp socket containing electrical circuitry for variably brightening and dimming the electrical circuit current supplied to a lamp within the socket. The electronic circuitry is comprised of oppositely poled silicon-controlled rectifiers (SCRs) connected to Zener diodes and a phasing circuit having a plurality of capacitors and variable resistance in series across the SCRs. An object of the invention is to provide means of controlling the light intensity of incandescent lamps “without the use of bulky rheostats which dissipate power that is expensive and heat which creates a problem to remove.”
In addition to being in convenient, use of the wrong bulb in a given socket may be dangerous. Many fixtures specify that only bulbs up to a particular wattage may be used, and that higher-wattage bulbs may result in a fire hazard. U.S. Pat. No. 7,234,973 solves this problem mechanically. FIG. 3 illustrates a modified light bulb base according to this patent where the contact at the bottom of the bulb base is specifically sized to be small, typically 3 millimeters (mm) in diameter. FIG. 4 illustrates a modified light bulb base where the contact at the bottom of the bulb base is 8 mm in diameter. FIG. 5 illustrates a modified light bulb base where the contact at the bottom of the bulb base is 13 mm in diameter.
Each bulb base 200 includes the standard sized threaded base 201, an insulative material 203 and a center contact 205a, 205b, or 205c specifically sized so as to operate with a specific type of luminare socket. As seen in FIGS. 3-5, the size of the contact 205a, 205b, or 205c will vary with the wattage of the bulb. Thus, a light bulb greater than 100 watts will feature a small contact 205c which has a diameter typically 3 mm in size. A bulb between 61 watts and 100 watts will use a slightly larger contact 205b with a diameter that is approximately 8 mm in size while a bulb 60 watts or less will use the largest contact 205a that is approximately 13 mm in diameter.
While the '973 patent addresses the compatibility issue, as admitted in the disclosure, “the invention involves modifying both the light bulb base as well as the luminare socket used with the base.” Given the vast, installed infrastructure, particularly of Edison-style bulbs, the wholesale modification of bulbs and sockets would take considerable time, if successful. Accordingly, the need remains for universality without bulb modification, if possible.